1. Field of the Invention
The present invention relates to an automatic dialer which generates a signal for selecting a communication line used by a plurality of common carriers.
2. Description of the Prior Art
FIG. 1 shows two signal paths for connecting a calling side telephone set 1 and a called side telephone set 90. In FIG. 1, reference numerals 2 and 200 designate telephone switchboards belonging to a first common carrier, which are coupled to two telephone sets 1 and 90. Reference numerals 3 and 300 designate telephone switchboards belonging to a second common carrier. A communication line 2C for connecting directly between the two telephone switchboards 2 and 200 belongs to the first common carrier and a communication line 2D for connecting directly between the other two telephone switchboards 3 and 300 belongs to the second common carrier. The other communication lines 2A, 2B, 2E, and 2F belong to the first common carrier. As shown in FIG. 1, a first signal path is composed of the communication line 2A, switch board 2, communication line 2C, switchboard 200 and communication line 2F and a second signal path is composed of the communication line 2A, switchboard 2, communication line 2B, switchboard 3, communication line 2D, switchboard 300, communication line 2E, switchboard 200 and communication line 2F.
The first signal path is a normal basic path. Therefore, when the first signal path is used, the communication from the calling side telephone set 1 to the called side telephone set 90 can be made only by means of dialing a toll number, a local office number, and a subscriber's number.
When above-described second signal path is used, the telephone set 1 should be operated so as to dial a plurality of predetermined numbers (or symbols, if required) and to further dial a toll number, a local office number, and a subscriber's number. The dialing of the predetermined numbers is necessary to select the second signal path. In an existing switchboard, the calling side telephone set 1 needs to be recognized by the second common carrier. The predetermined numbers and/or symbols include a carrier calling number (i.e., an identification number for specifying the second common carrier), a service request code, and a subscriber's information number.
Other telephone systems contain a device to automatically generate a signal for specifying one of such a plurality of signal paths. This device could be, for example, a "SYSTEM 4000 TELEFLEX" produced by COMMUNICATIONS SYSTEMS, INC.
Such a device is provided on a cable between the telephone set and the telephone switchboard. However, such a device is extremely troublesome in handling. More specifically, the device contains a memory storing a program corresponding to a signal path and individual information relating to the calling side telephone. Moreover, the device is required to store I.D. codes so as to transmit a signal corresponding to a telephone switchboard in an area where the device is located. Thus, this device is programmed by a personal computer through a modem, thereby operations of a plurality of dip switches of this device are needed.
Furthermore, if a user wishes to change toll numbers, that are handled by some common carriers, it is necessary to rewrite a corresponding program in the device by a personal computer through a modem.